Using boring machines for drilling horizontal bore holes under a roadway or other obstruction is a well known practice. The process of providing such horizontal bore holes is often generally referred to as "trenchless" digging, since an open trench is not required. When high pressure sprays are used in connection with such boring mechanism to control the direction of drilling, it is often called "directional boring". A boring string comprises connected links of pipe that drive the boring drill bit blade while providing fluid under pressure to the blade for cooling or steering, or both. One example of a directional boring system is available from bor-mor, Inc., Lino Lakes, Minn. This system is described in detail in U.S. Pat. No. 5,226,488 to Lessard, et al., entitled "Truck Mounted Boring System", which is assigned to the same assignee as the present invention, the teachings of which are incorporated herein by reference.
Some other examples of horizontal boring mechanisms including known boring drill bit blade designs are disclosed in U.S. Pat. No. 5,148,880 issued Sep. 22, 1993 to Lee, et al. In that invention, a boring drill bit blade assembly is disclosed as being affixed to the front of a tapered portion of a tool body. Fluid is injected from the tool body through a nozzle and impinges on the outer surface of the boring drill bit blade to aid in the drilling action by cooling and lubricating the boring drill bit blade.
Boring drill bit blades currently used with directional boring machines for drilling horizontal bore holes have an extremely limited life span due at least in part to overheating during boring. Known boring drill bit blade designs, as disclosed in the Lee, et al. patent, teach that a stream of fluid is directed from a tool body to an exterior surface of the boring drill bit blade. Such a design positions the high pressure spray nozzle a significant distance behind the cutting edge of the boring drill bit blade. It is believed that the more distance that exists between the cutting edge and the nozzle, the less effective the jet stream of fluid will be in steering a boring string.
One motive of this invention is to provide a means to quickly and efficiently cool and steer bore hole boring drill bit blades through the means of internal fluid conduit and spray mechanisms.